An Outbreak of Human Coronavirus OC43 during the 2014–2015 Influenza Season in Yamagata, Japan

Abstract

Coronaviruses are enveloped, positive-sense, singlestrand RNA viruses that belong to the subfamily Coronavirinae in the family Coronaviridae (1). Six coronaviruses are known to infect humans: human coronaviruses (HCoV-229E, -OC43, -NL63, -HKU1), severe acute respiratory syndrome coronavirus (SARS-CoV), and Middle East respiratory syndrome coronavirus (MERS-CoV). Four of these viruses (HCoV-229E, -OC43, -NL63, and -HKU1) are known to circulate continuously in the human population (1) and have been detected in the Japanese population while SARS-CoV and MERS-CoV have not. While HCoVs are associated with respiratory symptoms ranging from mild upper respiratory tract infections to severe lower respiratory tract infections including pneumonia and bronchiolitis (1,2), previous HCoV research has been hampered by a lack of observable cytopathic effects and poor growth in cell cultures. However, increasingly sensitive detection methods, such as reverse-transcription polymerase chain reaction (RT-PCR) assays, can now identify previously undetected cases (2-11).